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Subject[PATCH v4.14] usb: gadget: f_fs: Fix setting of device and driver data cross-references
Date
FunctionFS device structure 'struct ffs_dev' and driver data structure
'struct ffs_data' are bound to each other with cross-reference pointers
'ffs_data->private_data' and 'ffs_dev->ffs_data'. While the first one
is supposed to be valid through the whole life of 'struct ffs_data'
(and while 'struct ffs_dev' exists non-freed), the second one is cleared
in 'ffs_closed()' (called from 'ffs_data_reset()' or the last
'ffs_data_put()'). This can be called several times, alternating in
different order with 'ffs_free_inst()', that, if possible, clears
the other cross-reference.

As a result, different cases of these calls order may leave stale
cross-reference pointers, used when the pointed structure is already
freed. Even if it occasionally doesn't cause kernel crash, this error
is reported by KASAN-enabled kernel configuration.

For example, the case [last 'ffs_data_put()' - 'ffs_free_inst()'] was
fixed by commit cdafb6d8b8da ("usb: gadget: f_fs: Fix use-after-free in
ffs_free_inst").

The other case ['ffs_data_reset()' - 'ffs_free_inst()' - 'ffs_data_put()']
now causes KASAN reported error [1], when 'ffs_data_reset()' clears
'ffs_dev->ffs_data', then 'ffs_free_inst()' frees the 'struct ffs_dev',
but can't clear 'ffs_data->private_data', which is then accessed
in 'ffs_closed()' called from 'ffs_data_put()'. This happens since
'ffs_dev->ffs_data' reference is cleared too early.

Moreover, one more use case, when 'ffs_free_inst()' is called immediately
after mounting FunctionFS device (that is before the descriptors are
written and 'ffs_ready()' is called), and then 'ffs_data_reset()'
or 'ffs_data_put()' is called from accessing "ep0" file or unmounting
the device. This causes KASAN error report like [2], since
'ffs_dev->ffs_data' is not yet set when 'ffs_free_inst()' can't properly
clear 'ffs_data->private_data', that is later accessed to freed structure.

Fix these (and may be other) cases of stale pointers access by moving
setting and clearing of the mentioned cross-references to the single
places, setting both of them when 'struct ffs_data' is created and
bound to 'struct ffs_dev', and clearing both of them when one of the
structures is destroyed. It seems convenient to make this pointer
initialization and structures binding in 'ffs_acquire_dev()' and
make pointers clearing in 'ffs_release_dev()'. This required some
changes in these functions parameters and return types.

Also, 'ffs_release_dev()' calling requires some cleanup, fixing minor
issues, like (1) 'ffs_release_dev()' is not called if 'ffs_free_inst()'
is called without unmounting the device, and "release_dev" callback
is not called at all, or (2) "release_dev" callback is called before
"ffs_closed" callback on unmounting, which seems to be not correctly
nested with "acquire_dev" and "ffs_ready" callbacks.
Make this cleanup togther with other mentioned 'ffs_release_dev()' changes.

[1]
==================================================================
root@rcar-gen3:~# mkdir /dev/cfs
root@rcar-gen3:~# mkdir /dev/ffs
root@rcar-gen3:~# modprobe libcomposite
root@rcar-gen3:~# mount -t configfs none /dev/cfs
root@rcar-gen3:~# mkdir /dev/cfs/usb_gadget/g1
root@rcar-gen3:~# mkdir /dev/cfs/usb_gadget/g1/functions/ffs.ffs
[ 64.340664] file system registered
root@rcar-gen3:~# mount -t functionfs ffs /dev/ffs
root@rcar-gen3:~# cd /dev/ffs
root@rcar-gen3:/dev/ffs# /home/root/ffs-test
ffs-test: info: ep0: writing descriptors (in v2 format)
[ 83.181442] read descriptors
[ 83.186085] read strings
ffs-test: info: ep0: writing strings
ffs-test: dbg: ep1: starting
ffs-test: dbg: ep2: starting
ffs-test: info: ep1: starts
ffs-test: info: ep2: starts
ffs-test: info: ep0: starts

^C
root@rcar-gen3:/dev/ffs# cd /home/root/
root@rcar-gen3:~# rmdir /dev/cfs/usb_gadget/g1/functions/ffs.ffs
[ 98.935061] unloading
root@rcar-gen3:~# umount /dev/ffs
[ 102.734301] ==================================================================
[ 102.742059] BUG: KASAN: use-after-free in ffs_release_dev+0x64/0xa8 [usb_f_fs]
[ 102.749683] Write of size 1 at addr ffff0004d46ff549 by task umount/2997
[ 102.756709]
[ 102.758311] CPU: 0 PID: 2997 Comm: umount Not tainted 5.13.0-rc4+ #8
[ 102.764971] Hardware name: Renesas Salvator-X board based on r8a77951 (DT)
[ 102.772179] Call trace:
[ 102.774779] dump_backtrace+0x0/0x330
[ 102.778653] show_stack+0x20/0x2c
[ 102.782152] dump_stack+0x11c/0x1ac
[ 102.785833] print_address_description.constprop.0+0x30/0x274
[ 102.791862] kasan_report+0x14c/0x1c8
[ 102.795719] __asan_report_store1_noabort+0x34/0x58
[ 102.800840] ffs_release_dev+0x64/0xa8 [usb_f_fs]
[ 102.805801] ffs_fs_kill_sb+0x50/0x84 [usb_f_fs]
[ 102.810663] deactivate_locked_super+0xa0/0xf0
[ 102.815339] deactivate_super+0x98/0xac
[ 102.819378] cleanup_mnt+0xd0/0x1b0
[ 102.823057] __cleanup_mnt+0x1c/0x28
[ 102.826823] task_work_run+0x104/0x180
[ 102.830774] do_notify_resume+0x458/0x14e0
[ 102.835083] work_pending+0xc/0x5f8
[ 102.838762]
[ 102.840357] Allocated by task 2988:
[ 102.844032] kasan_save_stack+0x28/0x58
[ 102.848071] kasan_set_track+0x28/0x3c
[ 102.852016] ____kasan_kmalloc+0x84/0x9c
[ 102.856142] __kasan_kmalloc+0x10/0x1c
[ 102.860088] __kmalloc+0x214/0x2f8
[ 102.863678] kzalloc.constprop.0+0x14/0x20 [usb_f_fs]
[ 102.868990] ffs_alloc_inst+0x8c/0x208 [usb_f_fs]
[ 102.873942] try_get_usb_function_instance+0xf0/0x164 [libcomposite]
[ 102.880629] usb_get_function_instance+0x64/0x68 [libcomposite]
[ 102.886858] function_make+0x128/0x1ec [libcomposite]
[ 102.892185] configfs_mkdir+0x330/0x590 [configfs]
[ 102.897245] vfs_mkdir+0x12c/0x1bc
[ 102.900835] do_mkdirat+0x180/0x1d0
[ 102.904513] __arm64_sys_mkdirat+0x80/0x94
[ 102.908822] invoke_syscall+0xf8/0x25c
[ 102.912772] el0_svc_common.constprop.0+0x150/0x1a0
[ 102.917891] do_el0_svc+0xa0/0xd4
[ 102.921386] el0_svc+0x24/0x34
[ 102.924613] el0_sync_handler+0xcc/0x154
[ 102.928743] el0_sync+0x198/0x1c0
[ 102.932238]
[ 102.933832] Freed by task 2996:
[ 102.937144] kasan_save_stack+0x28/0x58
[ 102.941181] kasan_set_track+0x28/0x3c
[ 102.945128] kasan_set_free_info+0x28/0x4c
[ 102.949435] ____kasan_slab_free+0x104/0x118
[ 102.953921] __kasan_slab_free+0x18/0x24
[ 102.958047] slab_free_freelist_hook+0x148/0x1f0
[ 102.962897] kfree+0x318/0x440
[ 102.966123] ffs_free_inst+0x164/0x2d8 [usb_f_fs]
[ 102.971075] usb_put_function_instance+0x84/0xa4 [libcomposite]
[ 102.977302] ffs_attr_release+0x18/0x24 [usb_f_fs]
[ 102.982344] config_item_put+0x140/0x1a4 [configfs]
[ 102.987486] configfs_rmdir+0x3fc/0x518 [configfs]
[ 102.992535] vfs_rmdir+0x114/0x234
[ 102.996122] do_rmdir+0x274/0x2b0
[ 102.999617] __arm64_sys_unlinkat+0x94/0xc8
[ 103.004015] invoke_syscall+0xf8/0x25c
[ 103.007961] el0_svc_common.constprop.0+0x150/0x1a0
[ 103.013080] do_el0_svc+0xa0/0xd4
[ 103.016575] el0_svc+0x24/0x34
[ 103.019801] el0_sync_handler+0xcc/0x154
[ 103.023930] el0_sync+0x198/0x1c0
[ 103.027426]
[ 103.029020] The buggy address belongs to the object at ffff0004d46ff500
[ 103.029020] which belongs to the cache kmalloc-128 of size 128
[ 103.042079] The buggy address is located 73 bytes inside of
[ 103.042079] 128-byte region [ffff0004d46ff500, ffff0004d46ff580)
[ 103.054236] The buggy address belongs to the page:
[ 103.059262] page:0000000021aa849b refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff0004d46fee00 pfn:0x5146fe
[ 103.070437] head:0000000021aa849b order:1 compound_mapcount:0
[ 103.076456] flags: 0x8000000000010200(slab|head|zone=2)
[ 103.081948] raw: 8000000000010200 fffffc0013521a80 0000000d0000000d ffff0004c0002300
[ 103.090052] raw: ffff0004d46fee00 000000008020001e 00000001ffffffff 0000000000000000
[ 103.098150] page dumped because: kasan: bad access detected
[ 103.103985]
[ 103.105578] Memory state around the buggy address:
[ 103.110602] ffff0004d46ff400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 103.118161] ffff0004d46ff480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 103.125726] >ffff0004d46ff500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 103.133284] ^
[ 103.139120] ffff0004d46ff580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 103.146679] ffff0004d46ff600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 103.154238] ==================================================================
[ 103.161792] Disabling lock debugging due to kernel taint
[ 103.167319] Unable to handle kernel paging request at virtual address 0037801d6000018e
[ 103.175406] Mem abort info:
[ 103.178457] ESR = 0x96000004
[ 103.181609] EC = 0x25: DABT (current EL), IL = 32 bits
[ 103.187020] SET = 0, FnV = 0
[ 103.190185] EA = 0, S1PTW = 0
[ 103.193417] Data abort info:
[ 103.196385] ISV = 0, ISS = 0x00000004
[ 103.200315] CM = 0, WnR = 0
[ 103.203366] [0037801d6000018e] address between user and kernel address ranges
[ 103.210611] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 103.216231] Modules linked in: usb_f_fs libcomposite configfs ath9k_htc led_class mac80211 libarc4 ath9k_common ath9k_hw ath cfg80211 aes_ce_blk sata_rc4
[ 103.259233] CPU: 0 PID: 2997 Comm: umount Tainted: G B 5.13.0-rc4+ #8
[ 103.267031] Hardware name: Renesas Salvator-X board based on r8a77951 (DT)
[ 103.273951] pstate: 00000005 (nzcv daif -PAN -UAO -TCO BTYPE=--)
[ 103.280001] pc : ffs_data_clear+0x138/0x370 [usb_f_fs]
[ 103.285197] lr : ffs_data_clear+0x124/0x370 [usb_f_fs]
[ 103.290385] sp : ffff800014777a80
[ 103.293725] x29: ffff800014777a80 x28: ffff0004d7649c80 x27: 0000000000000000
[ 103.300931] x26: ffff800014777fb0 x25: ffff60009aec9394 x24: ffff0004d7649ca4
[ 103.308136] x23: 1fffe0009a3d063a x22: dfff800000000000 x21: ffff0004d1e831d0
[ 103.315340] x20: e1c000eb00000bb4 x19: ffff0004d1e83000 x18: 0000000000000000
[ 103.322545] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[ 103.329748] x14: 0720072007200720 x13: 0720072007200720 x12: 1ffff000012ef658
[ 103.336952] x11: ffff7000012ef658 x10: 0720072007200720 x9 : ffff800011322648
[ 103.344157] x8 : ffff800014777818 x7 : ffff80000977b2c7 x6 : 0000000000000000
[ 103.351359] x5 : 0000000000000001 x4 : ffff7000012ef659 x3 : 0000000000000001
[ 103.358562] x2 : 0000000000000000 x1 : 1c38001d6000018e x0 : e1c000eb00000c70
[ 103.365766] Call trace:
[ 103.368235] ffs_data_clear+0x138/0x370 [usb_f_fs]
[ 103.373076] ffs_data_reset+0x20/0x304 [usb_f_fs]
[ 103.377829] ffs_data_closed+0x1ec/0x244 [usb_f_fs]
[ 103.382755] ffs_fs_kill_sb+0x70/0x84 [usb_f_fs]
[ 103.387420] deactivate_locked_super+0xa0/0xf0
[ 103.391905] deactivate_super+0x98/0xac
[ 103.395776] cleanup_mnt+0xd0/0x1b0
[ 103.399299] __cleanup_mnt+0x1c/0x28
[ 103.402906] task_work_run+0x104/0x180
[ 103.406691] do_notify_resume+0x458/0x14e0
[ 103.410823] work_pending+0xc/0x5f8
[ 103.414351] Code: b4000a54 9102f280 12000802 d343fc01 (38f66821)
[ 103.420490] ---[ end trace 57b43a50e8244f57 ]---
Segmentation fault
root@rcar-gen3:~#
==================================================================

[2]
==================================================================
root@rcar-gen3:~# mkdir /dev/ffs
root@rcar-gen3:~# modprobe libcomposite
root@rcar-gen3:~#
root@rcar-gen3:~# mount -t configfs none /dev/cfs
root@rcar-gen3:~# mkdir /dev/cfs/usb_gadget/g1
root@rcar-gen3:~# mkdir /dev/cfs/usb_gadget/g1/functions/ffs.ffs
[ 54.766480] file system registered
root@rcar-gen3:~# mount -t functionfs ffs /dev/ffs
root@rcar-gen3:~# rmdir /dev/cfs/usb_gadget/g1/functions/ffs.ffs
[ 63.197597] unloading
root@rcar-gen3:~# cat /dev/ffs/ep0
cat: read error:[ 67.213506] ==================================================================
[ 67.222095] BUG: KASAN: use-after-free in ffs_data_clear+0x70/0x370 [usb_f_fs]
[ 67.229699] Write of size 1 at addr ffff0004c26e974a by task cat/2994
[ 67.236446]
[ 67.238045] CPU: 0 PID: 2994 Comm: cat Not tainted 5.13.0-rc4+ #8
[ 67.244431] Hardware name: Renesas Salvator-X board based on r8a77951 (DT)
[ 67.251624] Call trace:
[ 67.254212] dump_backtrace+0x0/0x330
[ 67.258081] show_stack+0x20/0x2c
[ 67.261579] dump_stack+0x11c/0x1ac
[ 67.265260] print_address_description.constprop.0+0x30/0x274
[ 67.271286] kasan_report+0x14c/0x1c8
[ 67.275143] __asan_report_store1_noabort+0x34/0x58
[ 67.280265] ffs_data_clear+0x70/0x370 [usb_f_fs]
[ 67.285220] ffs_data_reset+0x20/0x304 [usb_f_fs]
[ 67.290172] ffs_data_closed+0x240/0x244 [usb_f_fs]
[ 67.295305] ffs_ep0_release+0x40/0x54 [usb_f_fs]
[ 67.300256] __fput+0x304/0x580
[ 67.303576] ____fput+0x18/0x24
[ 67.306893] task_work_run+0x104/0x180
[ 67.310846] do_notify_resume+0x458/0x14e0
[ 67.315154] work_pending+0xc/0x5f8
[ 67.318834]
[ 67.320429] Allocated by task 2988:
[ 67.324105] kasan_save_stack+0x28/0x58
[ 67.328144] kasan_set_track+0x28/0x3c
[ 67.332090] ____kasan_kmalloc+0x84/0x9c
[ 67.336217] __kasan_kmalloc+0x10/0x1c
[ 67.340163] __kmalloc+0x214/0x2f8
[ 67.343754] kzalloc.constprop.0+0x14/0x20 [usb_f_fs]
[ 67.349066] ffs_alloc_inst+0x8c/0x208 [usb_f_fs]
[ 67.354017] try_get_usb_function_instance+0xf0/0x164 [libcomposite]
[ 67.360705] usb_get_function_instance+0x64/0x68 [libcomposite]
[ 67.366934] function_make+0x128/0x1ec [libcomposite]
[ 67.372260] configfs_mkdir+0x330/0x590 [configfs]
[ 67.377320] vfs_mkdir+0x12c/0x1bc
[ 67.380911] do_mkdirat+0x180/0x1d0
[ 67.384589] __arm64_sys_mkdirat+0x80/0x94
[ 67.388899] invoke_syscall+0xf8/0x25c
[ 67.392850] el0_svc_common.constprop.0+0x150/0x1a0
[ 67.397969] do_el0_svc+0xa0/0xd4
[ 67.401464] el0_svc+0x24/0x34
[ 67.404691] el0_sync_handler+0xcc/0x154
[ 67.408819] el0_sync+0x198/0x1c0
[ 67.412315]
[ 67.413909] Freed by task 2993:
[ 67.417220] kasan_save_stack+0x28/0x58
[ 67.421257] kasan_set_track+0x28/0x3c
[ 67.425204] kasan_set_free_info+0x28/0x4c
[ 67.429513] ____kasan_slab_free+0x104/0x118
[ 67.434001] __kasan_slab_free+0x18/0x24
[ 67.438128] slab_free_freelist_hook+0x148/0x1f0
[ 67.442978] kfree+0x318/0x440
[ 67.446205] ffs_free_inst+0x164/0x2d8 [usb_f_fs]
[ 67.451156] usb_put_function_instance+0x84/0xa4 [libcomposite]
[ 67.457385] ffs_attr_release+0x18/0x24 [usb_f_fs]
[ 67.462428] config_item_put+0x140/0x1a4 [configfs]
[ 67.467570] configfs_rmdir+0x3fc/0x518 [configfs]
[ 67.472626] vfs_rmdir+0x114/0x234
[ 67.476215] do_rmdir+0x274/0x2b0
[ 67.479710] __arm64_sys_unlinkat+0x94/0xc8
[ 67.484108] invoke_syscall+0xf8/0x25c
[ 67.488055] el0_svc_common.constprop.0+0x150/0x1a0
[ 67.493175] do_el0_svc+0xa0/0xd4
[ 67.496671] el0_svc+0x24/0x34
[ 67.499896] el0_sync_handler+0xcc/0x154
[ 67.504024] el0_sync+0x198/0x1c0
[ 67.507520]
[ 67.509114] The buggy address belongs to the object at ffff0004c26e9700
[ 67.509114] which belongs to the cache kmalloc-128 of size 128
[ 67.522171] The buggy address is located 74 bytes inside of
[ 67.522171] 128-byte region [ffff0004c26e9700, ffff0004c26e9780)
[ 67.534328] The buggy address belongs to the page:
[ 67.539355] page:000000003177a217 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5026e8
[ 67.549175] head:000000003177a217 order:1 compound_mapcount:0
[ 67.555195] flags: 0x8000000000010200(slab|head|zone=2)
[ 67.560687] raw: 8000000000010200 fffffc0013037100 0000000c00000002 ffff0004c0002300
[ 67.568791] raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000
[ 67.576890] page dumped because: kasan: bad access detected
[ 67.582725]
[ 67.584318] Memory state around the buggy address:
[ 67.589343] ffff0004c26e9600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 67.596903] ffff0004c26e9680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 67.604463] >ffff0004c26e9700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 67.612022] ^
[ 67.617860] ffff0004c26e9780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 67.625421] ffff0004c26e9800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 67.632981] ==================================================================
[ 67.640535] Disabling lock debugging due to kernel taint
File descriptor[ 67.646100] Unable to handle kernel paging request at virtual address fabb801d4000018d
in bad state
[ 67.655456] Mem abort info:
[ 67.659619] ESR = 0x96000004
[ 67.662801] EC = 0x25: DABT (current EL), IL = 32 bits
[ 67.668225] SET = 0, FnV = 0
[ 67.671375] EA = 0, S1PTW = 0
[ 67.674613] Data abort info:
[ 67.677587] ISV = 0, ISS = 0x00000004
[ 67.681522] CM = 0, WnR = 0
[ 67.684588] [fabb801d4000018d] address between user and kernel address ranges
[ 67.691849] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 67.697470] Modules linked in: usb_f_fs libcomposite configfs ath9k_htc led_class mac80211 libarc4 ath9k_common ath9k_hw ath cfg80211 aes_ce_blk crypto_simd cryptd aes_ce_cipher ghash_ce gf128mul sha2_ce sha1_ce evdev sata_rcar libata xhci_plat_hcd scsi_mod xhci_hcd rene4
[ 67.740467] CPU: 0 PID: 2994 Comm: cat Tainted: G B 5.13.0-rc4+ #8
[ 67.748005] Hardware name: Renesas Salvator-X board based on r8a77951 (DT)
[ 67.754924] pstate: 00000005 (nzcv daif -PAN -UAO -TCO BTYPE=--)
[ 67.760974] pc : ffs_data_clear+0x138/0x370 [usb_f_fs]
[ 67.766178] lr : ffs_data_clear+0x124/0x370 [usb_f_fs]
[ 67.771365] sp : ffff800014767ad0
[ 67.774706] x29: ffff800014767ad0 x28: ffff800009cf91c0 x27: ffff0004c54861a0
[ 67.781913] x26: ffff0004dc90b288 x25: 1fffe00099ec10f5 x24: 00000000000a801d
[ 67.789118] x23: 1fffe00099f6953a x22: dfff800000000000 x21: ffff0004cfb4a9d0
[ 67.796322] x20: d5e000ea00000bb1 x19: ffff0004cfb4a800 x18: 0000000000000000
[ 67.803526] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[ 67.810730] x14: 0720072007200720 x13: 0720072007200720 x12: 1ffff000028ecefa
[ 67.817934] x11: ffff7000028ecefa x10: 0720072007200720 x9 : ffff80001132c014
[ 67.825137] x8 : ffff8000147677d8 x7 : ffff8000147677d7 x6 : 0000000000000000
[ 67.832341] x5 : 0000000000000001 x4 : ffff7000028ecefb x3 : 0000000000000001
[ 67.839544] x2 : 0000000000000005 x1 : 1abc001d4000018d x0 : d5e000ea00000c6d
[ 67.846748] Call trace:
[ 67.849218] ffs_data_clear+0x138/0x370 [usb_f_fs]
[ 67.854058] ffs_data_reset+0x20/0x304 [usb_f_fs]
[ 67.858810] ffs_data_closed+0x240/0x244 [usb_f_fs]
[ 67.863736] ffs_ep0_release+0x40/0x54 [usb_f_fs]
[ 67.868488] __fput+0x304/0x580
[ 67.871665] ____fput+0x18/0x24
[ 67.874837] task_work_run+0x104/0x180
[ 67.878622] do_notify_resume+0x458/0x14e0
[ 67.882754] work_pending+0xc/0x5f8
[ 67.886282] Code: b4000a54 9102f280 12000802 d343fc01 (38f66821)
[ 67.892422] ---[ end trace 6d7cedf53d7abbea ]---
Segmentation fault
root@rcar-gen3:~#
==================================================================

Fixes: 4b187fceec3c ("usb: gadget: FunctionFS: add devices management code")
Fixes: 3262ad824307 ("usb: gadget: f_fs: Stop ffs_closed NULL pointer dereference")
Fixes: cdafb6d8b8da ("usb: gadget: f_fs: Fix use-after-free in ffs_free_inst")
Reported-by: Bhuvanesh Surachari <bhuvanesh_surachari@mentor.com>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Link: https://lore.kernel.org/r/20210603171507.22514-1-andrew_gabbasov@mentor.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-picked from commit ecfbd7b9054bddb12cea07fda41bb3a79a7b0149)
[agabbasov: Backported to earlier mount API, resolved context conflicts]
---
drivers/usb/gadget/function/f_fs.c | 67 ++++++++++++++----------------
1 file changed, 32 insertions(+), 35 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 458c5dc296ac..5dfe926c251a 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -247,8 +247,8 @@ EXPORT_SYMBOL_GPL(ffs_lock);
static struct ffs_dev *_ffs_find_dev(const char *name);
static struct ffs_dev *_ffs_alloc_dev(void);
static void _ffs_free_dev(struct ffs_dev *dev);
-static void *ffs_acquire_dev(const char *dev_name);
-static void ffs_release_dev(struct ffs_data *ffs_data);
+static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data);
+static void ffs_release_dev(struct ffs_dev *ffs_dev);
static int ffs_ready(struct ffs_data *ffs);
static void ffs_closed(struct ffs_data *ffs);

@@ -1505,7 +1505,6 @@ ffs_fs_mount(struct file_system_type *t, int flags,
};
struct dentry *rv;
int ret;
- void *ffs_dev;
struct ffs_data *ffs;

ENTER();
@@ -1526,19 +1525,16 @@ ffs_fs_mount(struct file_system_type *t, int flags,
return ERR_PTR(-ENOMEM);
}

- ffs_dev = ffs_acquire_dev(dev_name);
- if (IS_ERR(ffs_dev)) {
+ ret = ffs_acquire_dev(dev_name, ffs);
+ if (ret) {
ffs_data_put(ffs);
- return ERR_CAST(ffs_dev);
+ return ERR_PTR(ret);
}
- ffs->private_data = ffs_dev;
data.ffs_data = ffs;

rv = mount_nodev(t, flags, &data, ffs_sb_fill);
- if (IS_ERR(rv) && data.ffs_data) {
- ffs_release_dev(data.ffs_data);
+ if (IS_ERR(rv) && data.ffs_data)
ffs_data_put(data.ffs_data);
- }
return rv;
}

@@ -1548,10 +1544,8 @@ ffs_fs_kill_sb(struct super_block *sb)
ENTER();

kill_litter_super(sb);
- if (sb->s_fs_info) {
- ffs_release_dev(sb->s_fs_info);
+ if (sb->s_fs_info)
ffs_data_closed(sb->s_fs_info);
- }
}

static struct file_system_type ffs_fs_type = {
@@ -1620,6 +1614,7 @@ static void ffs_data_put(struct ffs_data *ffs)
if (unlikely(refcount_dec_and_test(&ffs->ref))) {
pr_info("%s(): freeing\n", __func__);
ffs_data_clear(ffs);
+ ffs_release_dev(ffs->private_data);
BUG_ON(waitqueue_active(&ffs->ev.waitq) ||
waitqueue_active(&ffs->ep0req_completion.wait) ||
waitqueue_active(&ffs->wait));
@@ -2924,6 +2919,7 @@ static inline struct f_fs_opts *ffs_do_functionfs_bind(struct usb_function *f,
struct ffs_function *func = ffs_func_from_usb(f);
struct f_fs_opts *ffs_opts =
container_of(f->fi, struct f_fs_opts, func_inst);
+ struct ffs_data *ffs_data;
int ret;

ENTER();
@@ -2938,12 +2934,13 @@ static inline struct f_fs_opts *ffs_do_functionfs_bind(struct usb_function *f,
if (!ffs_opts->no_configfs)
ffs_dev_lock();
ret = ffs_opts->dev->desc_ready ? 0 : -ENODEV;
- func->ffs = ffs_opts->dev->ffs_data;
+ ffs_data = ffs_opts->dev->ffs_data;
if (!ffs_opts->no_configfs)
ffs_dev_unlock();
if (ret)
return ERR_PTR(ret);

+ func->ffs = ffs_data;
func->conf = c;
func->gadget = c->cdev->gadget;

@@ -3398,6 +3395,7 @@ static void ffs_free_inst(struct usb_function_instance *f)
struct f_fs_opts *opts;

opts = to_f_fs_opts(f);
+ ffs_release_dev(opts->dev);
ffs_dev_lock();
_ffs_free_dev(opts->dev);
ffs_dev_unlock();
@@ -3585,47 +3583,48 @@ static void _ffs_free_dev(struct ffs_dev *dev)
{
list_del(&dev->entry);

- /* Clear the private_data pointer to stop incorrect dev access */
- if (dev->ffs_data)
- dev->ffs_data->private_data = NULL;
-
kfree(dev);
if (list_empty(&ffs_devices))
functionfs_cleanup();
}

-static void *ffs_acquire_dev(const char *dev_name)
+static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data)
{
+ int ret = 0;
struct ffs_dev *ffs_dev;

ENTER();
ffs_dev_lock();

ffs_dev = _ffs_find_dev(dev_name);
- if (!ffs_dev)
- ffs_dev = ERR_PTR(-ENOENT);
- else if (ffs_dev->mounted)
- ffs_dev = ERR_PTR(-EBUSY);
- else if (ffs_dev->ffs_acquire_dev_callback &&
- ffs_dev->ffs_acquire_dev_callback(ffs_dev))
- ffs_dev = ERR_PTR(-ENOENT);
- else
+ if (!ffs_dev) {
+ ret = -ENOENT;
+ } else if (ffs_dev->mounted) {
+ ret = -EBUSY;
+ } else if (ffs_dev->ffs_acquire_dev_callback &&
+ ffs_dev->ffs_acquire_dev_callback(ffs_dev)) {
+ ret = -ENOENT;
+ } else {
ffs_dev->mounted = true;
+ ffs_dev->ffs_data = ffs_data;
+ ffs_data->private_data = ffs_dev;
+ }

ffs_dev_unlock();
- return ffs_dev;
+ return ret;
}

-static void ffs_release_dev(struct ffs_data *ffs_data)
+static void ffs_release_dev(struct ffs_dev *ffs_dev)
{
- struct ffs_dev *ffs_dev;
-
ENTER();
ffs_dev_lock();

- ffs_dev = ffs_data->private_data;
- if (ffs_dev) {
+ if (ffs_dev && ffs_dev->mounted) {
ffs_dev->mounted = false;
+ if (ffs_dev->ffs_data) {
+ ffs_dev->ffs_data->private_data = NULL;
+ ffs_dev->ffs_data = NULL;
+ }

if (ffs_dev->ffs_release_dev_callback)
ffs_dev->ffs_release_dev_callback(ffs_dev);
@@ -3653,7 +3652,6 @@ static int ffs_ready(struct ffs_data *ffs)
}

ffs_obj->desc_ready = true;
- ffs_obj->ffs_data = ffs;

if (ffs_obj->ffs_ready_callback) {
ret = ffs_obj->ffs_ready_callback(ffs);
@@ -3681,7 +3679,6 @@ static void ffs_closed(struct ffs_data *ffs)
goto done;

ffs_obj->desc_ready = false;
- ffs_obj->ffs_data = NULL;

if (test_and_clear_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags) &&
ffs_obj->ffs_closed_callback)
--
2.21.0
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